1. Field of the Invention
The invention relates to a tensioning means for hubs, comprising a winding shaft having rotatably and drivably mounted on it individual winding elements for hubs with inner cylindrical bores, the tensioning means including measures for locking in of the hubs in the axial direction on each individual winding element.
2. Description of the Related Art
In winding machines, in particular in combined longitudinal cutting and winding apparatuses, for example for magnetic tapes, the winding shafts in each case receive a large number of hubs. Fitting the winding shaft with hubs is problematical, since the numerous wound hubs are to be drawn off the winding shaft as quickly as possible and replaced in the correct position by empty hubs. The tensioning means should not hinder easy and troublefree displacing of the hubs on the shaft during fitting. Therefore, numerous tensioning means on the winding shaft are already known, such as tensioning rollers, tensioning pins or the like, which are mechanically complicated constructions which escalate the costs of the winding shaft. The difficulties become all the greater if individual winding elements with separate frictions are used.
In the Applicant's German application P 41 21 244, a number of tensioning means known from the prior art are described in detail. Similarly, in the said application a hub tensioning means of the generic type mentioned above is described, in which the tensioning means includes a plurality of segments which are distributed over the circumference of each cylindrical individual winding element, are seated in an annular groove and are loaded by spring elements. Furthermore, in this application FIGS. 6 and 7 show a snap-fitting or centering means for hubs, comprising a bead and a ball thrust piece on the outside of the tensioning means, which make it possible for the hubs to be pushed on axially and centered.
The said tensioning means have a number of disadvantages. Firstly, usually there is no accurate lateral fixing of the hubs. Secondly, the radially acting tensioning elements in the hub holder require a certain installation space, which often can be realized in the design only with difficulty since the hub holder also has to accommodate a stable mounting, which is as exact as possible, and devices suitable for torque generation, for example eddy-current couplings, for driving the individual winding elements.
Furthermore, a centering means for hubs is known, in which each hub has in its hub bore a central notch, in which a projection complementing it on the tensioning means engages. In this case it has been found that hubs with a notch are difficult to produce by injection molding, since they cannot be demolded easily, and producing a notch by machining, for example by turning, is very complicated and expensive.